Overview
Lead is a naturally occurring toxic metal found in the Earth’s crust. Its widespread use has resulted in extensive environmental contamination, human exposure and significant public health problems in many parts of the world.
Important sources of environmental contamination come from mining, smelting, manufacturing and recycling activities and use in a wide range of products. Most global lead consumption is for the manufacture of lead-acid batteries for motor vehicles. Lead is, however, also used in many other products, for example pigments, paints, solder, stained glass, lead crystal glassware, ammunition, ceramic glazes, jewellery, toys, some traditional cosmetics such as kohl and sindoor, and some traditional medicines used in countries such as India, Mexico and Viet Nam. Drinking water delivered through lead pipes or pipes joined with lead solder may contain lead. Much of the lead in global commerce is now obtained from recycling.
Young children are particularly vulnerable to the toxic effects of lead and can suffer profound and permanent adverse health impacts, particularly on the development of the brain and nervous system. Lead also causes long-term harm in adults, including increased risk of high blood pressure, cardiovascular problems and kidney damage. Exposure of pregnant women to high levels of lead can cause miscarriage, stillbirth, premature birth and low birth weight.
Sources and routes of exposure
People can become exposed to lead through occupational and environmental sources. This mainly results from:
- inhalation of lead particles generated by burning materials containing lead, for example during smelting, recycling, stripping leaded paint and plastic cables containing lead and using leaded aviation fuel; and
- ingestion of lead-contaminated dust, water (from leaded pipes) and food (from lead-glazed or lead-soldered containers) and from hand-to-mouth behaviour.
Young children are particularly vulnerable to lead poisoning because they absorb 4–5 times as much ingested lead as adults from a given source. Moreover, children’s innate curiosity and their age-appropriate hand-to-mouth behaviour result in their mouthing and swallowing lead-containing or lead-coated objects, such as contaminated soil or dust and flakes from decaying lead-containing paint. This route of exposure is magnified in children with a psychological disorder called pica (persistent and compulsive cravings to eat non-food items), who may pick away at and eat leaded paint from walls, door frames and furniture. Exposure to lead-contaminated soil and dust resulting from battery recycling and mining has caused mass lead poisoning and multiple deaths in young children in Nigeria, Senegal and other countries.
Once lead enters the body, it is distributed to organs such as the brain, kidneys, liver and bones. The body stores lead in the teeth and bones, where it accumulates over time. Lead stored in bone may be released into the blood during pregnancy, thus exposing the growing fetus Undernourished children are more susceptible to lead because their bodies absorb more lead if other nutrients, such as calcium or iron, are lacking. The very young are at the highest risk, as is the developing nervous system is a particularly vulnerable period
Health effects in children
Lead exposure can have serious consequences for the health of children. At high levels of exposure to lead the brain and central nervous system can be severely damaged causing coma, convulsions and even death. Children who survive severe lead poisoning may be left with permanent intellectual disability and behavioural disorders. At lower levels of exposure that cause no obvious symptoms, lead is now known to produce a spectrum of injury across multiple body systems. In particular, lead can affect children’s brain development, resulting in reduced intelligence quotient (IQ), behavioural changes such as reduced attention span and increased antisocial behaviour, and reduced educational attainment. Lead exposure also causes anaemia, hypertension, renal impairment, immunotoxicity and toxicity to the reproductive organs. The neurological and behavioural effects of lead are believed to be irreversible.
There is no known safe blood lead concentration; even blood lead concentrations as low as 3.5 µg/dL may be associated with decreased intelligence in children, behavioural difficulties and learning problems (1).
Burden of disease
The World Health Organization’s 2021 update of the Public health impact of chemicals: knowns and unknowns estimates that nearly half of the 2 million lives lost to known chemicals exposure in 2019 were due to exposure to lead. Lead exposure is estimated to account for 21.7 million years lost to disability and death (disability-adjusted life years, or DALYs) worldwide due to long-term effects on health, including 30% of the global burden of idiopathic intellectual disability, 4.6% of the global burden of cardiovascular disease and 3% of the global burden of chronic kidney diseases.
WHO response
WHO has identified lead as one of 10 chemicals of major public health concern needing action by Member States to protect the health of workers, children and women of reproductive age. WHO has made available through its website a range of information on lead, including information for policy-makers, technical guidance, training materials and advocacy materials. WHO has developed guidelines on clinical management of lead exposure and recommends that for an individual with a blood lead concentration ≥ 5 µg/dL, the source(s) of lead exposure should be identified, and appropriate action taken to reduce and terminate exposure.
The successful phasing out of leaded gasoline in most countries, together with other lead control measures, has confirmed significant public health benefits with a significant decline in population-level blood lead concentrations in many countries (2). As of July 2021, leaded fuel for cars and lorries is no longer sold anywhere in the world (3). However, more needs to be done to phase out lead paint; as of March 2023, only 48% of countries have introduced legally binding controls on lead paint.
Since leaded paint is a continuing source of exposure in many countries, WHO has joined with the United Nations Environment Programme to form the Global Alliance to Eliminate Lead Paint which has the aim of encouraging all countries to have legally binding laws to control the use of lead in paint. This goal has received further support in the WHO Chemicals Road map to enhance health sector engagement in the Strategic Approach to International Chemicals Management towards the 2020 goal and beyond (decision WHA70(23)), which includes national action to phase out the use of lead paint.
WHO is currently preparing guidelines on prevention of lead exposure, which will provide policy-makers, public health authorities and health professionals with evidence-based guidance on the measures that they can take to protect the health of children and adults from lead exposure.
References
(1) US CDC Advisory Committee on Childhood Lead Poisoning Prevention. CDC updates blood lead reference value to 3.5µg/dL. Atlanta: US Centres for Disease Control and Prevention; 2021 (https://www.cdc.gov/nceh/lead/news/cdc-updates-blood-lead-reference-value.html).
(2) End of leaded fuel use a “milestone for multilateralism” press release https://news.un.org/en/story/2021/08/1098792, 2021.
(3) Angrand et al. Relation of blood lead levels and lead in gasoline: an updated systematic review. Environmental Health (2022) 21:138 https://doi.org/10.1186/s12940-022-00936-x.
